^ I'll have to remember that, at the moment i'm not running mine 24/7... only planning on running it between my 50G and 60G tank when necessary, although its only mainly my 60G that seems to have problems which i guess is due in part to the frozen bloodworms i feed... my other tanks don't seem to have any of these problems so go figure?
But anyway, is that sponge special in any way? coz otherwise, i take it you could probably just cut any sponge to size and use it as a replacement as long as its porous enough not to slow the flow too much?